Megazeux is a game creation system that was created in 1995, by Greg Janson. It was quite similar to ZZT (By Epic Megagames), but had many new features such as an editible character set, color palette (although still limited to 16 colors), and a nice little programming language called robotic (originally called Robo-P, then changed to Robotic in Megazeux 2.0) that was very helpful in allowing people to actually make fun games.
Some games that are created with Megazeux are very impressive, considering that they're limited to text mode graphics. People have even attempted to create first person shooters with Megazeux, with varying amounts of success.
One Megazeux "company" (called Autumn Dreams) even figured out that you could create full motion video in Megazeux by putting all 256 characters in a grid and continuously loading a new character set for each frame of the "movie".
The current center of the megazeux community is at the website www.digitalmzx.net.